One of two men accused of massacring 33 dogs took potshots at a puppy as it tried to escape the bloodbath, a court has been told.

The Crown says Russell Mendoza and Tony Campbell went on a "commando exercise'' in January 2010, shooting 33 of their neighbour's dogs on a rural property north of Auckland.

The pair have denied four charges of wilfully ill-treating an animal.

The charges carry a maximum three years' imprisonment.

They have also pleaded not guilty to charges laid by police of reckless use of a firearm.

Opening the Crown's case today, prosecutor Joshua Shaw told Auckland District Court Mendoza organised the shooting because he believed his dog had been mauled by a dog belonging to Rowan Hargreaves, a neighbour.

Mr Shaw said Mendoza and Campbell went to Hargreaves' 5ha property near Wellsford. Mendoza took with him a note which he got Mr Hargreaves to sign saying the men could shoot the dogs and there would be "no comeback''.

He said the men found two dogs in a van and shot both of them in the head, making two "reasonably clean kills''.

They then went to a cage where eight dogs were kept and began shooting from both sides, Mr Shaw said.

"There was nothing clean or structured about it.''

He said dogs cowered behind other dogs or the cage structure in an attempt to take cover.

Mr Hargreaves could not watch and left but a friend stayed behind to see that the dogs were killed cleanly, Mr Shaw said.

"It was clear that they were not killed instantly. They suffered considerable stress as well as pain.''

The two men then moved to a campervan where more than 20 puppies were kept.

He said there was no suggestion that the puppies had been involved on the attack on Mendoza's dog.

"But for whatever reason, the accused were intent on killing every living dog in the campervan.''

One puppy escaped under the campervan and one of the men leaned under and took pot shots.

Mr Shaw said the shooting took up to 30 minutes.

"It seems, for the accused, it turned into something of a commando exercise ... after the first two dogs were killed, it really has been a case of killing every dog that was living.''

He said many of the dogs were not killed instantly or humanely with some suffering multiple injuries.

SPCA worker Sacha Keltie told the court she removed the bodies of eight dogs from a cage. The bodies of the puppies, some as young as four weeks, were found underneath a tarpaulin. All had bullet wounds.